The holiday is a significant one for both Lutheran and Calvinist churches, although other Protestant communities also tend to commemorate this day. The Catholic Church recognized it only recently, and often sends its official representatives in ecumenical spirit to various commemoration events held by Protestants. It is lawfully and officially recognized in some states of Germany and sovereign countries of Slovenia and Chile. In addition, countries like Switzerland and Austria provide specifics in laws pertaining to Protestant churches, while not officially proclaiming it a nationwide holiday.

On 31 October 1517, Martin Luther wrote to Albrecht, Archbishop of Mainz and Magdeburg, protesting against the sale of indulgences. He enclosed in his letter a copy of his "Disputation of Martin Luther on the Power and Efficacy of Indulgences", which came to be known as the Ninety-five Theses.[2] Hans Hillerbrand writes that Luther had no intention of confronting the church, but saw his disputation as a scholarly objection to church practices, and the tone of the writing is accordingly "searching, rather than doctrinaire."[3] Hillerbrand writes that there is nevertheless an undercurrent of challenge in several of the theses, particularly in Thesis 86, which asks: "Why does the pope, whose wealth today is greater than the wealth of the richest Crassus, build the basilica of St. Peter with the money of poor believers rather than with his own money?"[3]

Luther objected to a saying attributed to Johann Tetzel that "As soon as the coin in the coffer rings, the soul from purgatory [also attested as 'into heaven'] springs."[4] He insisted that, since forgiveness was God's alone to grant, those who claimed that indulgences absolved buyers from all punishments and granted them salvation were in error. Christians, he said, must not slacken in following Christ on account of such false assurances.

The sale of indulgences shown in A Question to a Mintmaker, woodcut by Jörg Breu the Elder of Augsburg, circa 1530.

According to Philipp Melanchthon, writing in 1546, Luther "wrote theses on indulgences and posted them on the church of All Saints on 31 October 1517", an event now seen as sparking the Reformation.[5] Some scholars have questioned Melanchthon's account, since he did not move to Wittenberg until a year later and no contemporaneous evidence exists for Luther's posting of the theses.[6] Others counter that such evidence is unnecessary because it was the custom at Wittenberg university to advertise a disputation by posting theses on the door of All Saints' Church, also known as "Castle Church".[7]

The Ninety-five Theses were quickly translated from Latin into German, printed, and widely copied, making the controversy one of the first in history to be aided by the printing press.[8] Within two weeks, copies of the theses had spread throughout Germany; within two months throughout Europe.

The parish order for the New Church in Regensburg states that the Reformation of the city is to be observed the first Sunday after October 15, every year. This document may be from 1567, however the dating is uncertain.[citation needed] The 1569 church order in Pomerania states that the Reformation was to be observed on St. Martin's Day, which falls on November 11. The hundredth anniversary of the Reformation, celebrated throughout the Protestant areas of Germany, was observed from October 31 to November 1, 1617, but a standard annual observance began much later, sometime after the two hundredth anniversary commemoration in 1717.

It is celebrated among various Protestants, especially by Lutheran and Reformed churches. Due to ecumenical movements, some other Christian groups tend to acknowledge or co-participate in church services celebrating the Reformation Day. That includes the Roman Catholic Church, as well as various Protestant denominations that are neither Lutheran nor Reformed, i.e. lack a connection to religious events of the 16th century Europe.

In the United States churches often transfer the holiday, so that it falls on the Sunday (called Reformation Sunday) on or before October 31, with All Saints' Day moved to the Sunday on or after November 1.[citation needed]

In 2013, the Joint International Commission between representatives of the Catholic Church and the Lutheran World Federation published a report entitled "From Conflict to Communion" anticipating the forthcoming "Lutheran-Catholic Common Commemoration of the Reformation in 2017", which noted that "in 2017, Lutheran and Catholic Christians will commemorate together the 500th anniversary of the beginning of the Reformation".[13] The "common commemoration" was a year-long remembrance concluded on Reformation Day 2017.[14]

In Germany, with the Reformation only ending more or less around 1648, and continued Catholic-Protestant animosity all over Europe well into the early 20th century, almost all of the following Reformation anniversaries were tainted by anti-Catholicism and nationalism: in 1617, the celebration of faith concentrated on Lutheran orthodoxy, and in 1717, too, the event focused on the liberation from the papal rule. Luther was celebrated as God's elected tool against the slavery of the new Roman Babylon. In 1817, the victory over Napoleon influenced the celebrations and lead to the anniversary's national orientation: Luther became the German hero and the ideal role model for the bourgeoisie; he was depicted time and again in festive parades and popular prints. The “German Luther” also drew wide attention in 1917 during the First World War when nationalist themes were still recurring; at the same time, serious research of Luther's theology gained increasing importance.

When the Lutheran areas of West Germany celebrated the Reformation anniversary in 1967, 450 years after the posting of the theses, the event took place during an “ice age” in the relationship between the state and the church in East Germany. This became clear through the attempt to secularise the Reformation with the concept of the “early bourgeois revolution” and through the pointed marginalisation of events organised by the church, for example by means of holding celebrations of the October Revolution at exactly the same time. In the Federal Republic of Germany there were only local celebrations, organised by the churches of the respective states. A central church event in Wittenberg on October 31, 1967, was held in order to keep up at least a pretence of an all-German Evangelical Church.

According to some sources, Reformation Day has been commemorated since 1567. Exact dates for the holiday varied until after the two hundredth celebration in 1717 when October 31 became the official date of celebration in Germany and later expanded internationally.[15][16]

Print made for the 1617 Reformation Jubilee showing Luther enscribing the Theses on the Wittenberg church door with a giant quill

In 1617, the celebration of faith concentrated on Lutheran orthodoxy.[17] In early 1617, the Lutheran duke and elector John George I of Saxony received a politically delicate dispatch. The University of Wittenberg asked for permission to celebrate the memory of its former lecturer Martin Luther. The duke agreed and made the commemoration obligatory for all of Electoral Saxony. The worship services and sermons were, however, all prewritten and prescribed in detail and provided as a recommendation to other Protestant regional rulers as well. They did not want any trouble with the Catholics.[18] In the end, the Reformation was celebrated in 1617 in nearly all of the Protestant territories of the Holy Roman Empire, and members of the Protestant Union and others following its lead all celebrated together on the first Sunday in November. As Wolfgang Flügel, an expert for Reformation jubilees and a researcher with the Society for Reformation History of the University of Halle-Wittenberg explains: “Competition and crises were decisive in the realization and content of the 1617 celebrations.” The historian Heinz Schilling speaks of “confrontation for the sake of preserving one’s own identity”.

1917 anniversary was held amidst the First World War. The theme of "German Luther" was rather silenced, marked by Germanophobia throughout the Anglo-Saxon world. In Germany, the anniversary was celebrated with nationalist elements.

The Lutheran World Federation (LWF) and Roman Catholic Church joint event will highlight the 50 years of continuous ecumenical dialogue between Catholics and Lutherans and the joint gifts of this collaboration. The Catholic-Lutheran commemoration of 500 years of the Reformation is structured around the themes of thanksgiving, repentance and commitment to common witness. The aim is to express the gifts of the Reformation and ask forgiveness for division perpetuated by Christians from the two traditions.[20]

An ecumenical service was presided over by Bishop Munib Younan, the president of the Lutheran World Federation, Martin Junge, the General Secretary of the LWF, as well as Pope Francis, the leader of the Catholic Church.[21] Representatives from the Anglican Communion, Baptist World Alliance, Eastern Orthodox Church, and Salvation Army also participated in the predominantly Lutheran and Roman Catholic event.[22] Pope Francis, in a joint statement with Bishop Munib A. Younan, stated that "With gratitude we acknowledge that the Reformation helped give a greater centrality to sacred Scripture in the church's life".[23]

October 31, 2017 was an official holiday in all of Germany.[24] As a legal basis, German states which usually do not celebrate Reformation Day annually passed legislation or made regulations. These states are Baden-Württemberg,[25] Bavaria,[26] Berlin,[27] Bremen,[28] Hamburg,[29] Hesse,[30] Lower Saxony,[31] North Rhine-Westphalia,[32] Rhineland-Palatinate,[33] Saarland[34] and Schleswig-Holstein.[35]

"I saw another angel fly in the midst of heaven, having the everlasting gospel to preach..."[39] This passage, traditionally interpreted as referring to Luther,[40] is commonly the text preached on during Reformation Day services.

Within the Lutheran church, Reformation Day is considered a lesser festival, and is officially referred to as The Festival of the Reformation. Until the 20th century, most Lutheran churches celebrated Reformation Day on October 31, regardless of which day of the week it occurred. Today, most Lutheran churches transfer the festival, so that it falls on the Sunday (called Reformation Sunday) on or before October 31 and transfer All Saints' Day to the Sunday on or after November 1.

The liturgical color of the day is red, which represents the Holy Spirit and the Martyrs of the Christian Church. Luther's hymn, "Ein feste Burg ist unser Gott" ("A Mighty Fortress is our God"), a paraphrase of Psalm 46, is traditionally sung on this day. It is also traditional in some Lutheran schools for schoolchildren to hold Reformation Day plays or pageants that re-enact scenes from the life of Martin Luther. The fact that Reformation Day coincides with Halloween is not mere coincidence. Halloween, being the Eve of All Saints' Day, might have been an entirely appropriate day for Luther to post his Ninety-five Theses against indulgences since the castle church would be open on All Saints' Day specifically for people to view a large collection of relics. The viewing of these relics was said to promise a reduction in time in purgatory similar to that of the purchase of an indulgence. That Martin Luther intended his Ninety-five Theses to persuade the common people, however, is extremely unlikely, since they were written in Latin, a language which the common people did not understand.

Although not shaped by Luther's doctrine, Calvinist churches throughout the world do not regard the Reformation Day as less important, and celebrate it in a similar manner to Lutherans. The nailing of the Ninety-five Theses sparked the discussion about Catholic beliefs and practices of the day. Reformed theology first emerged with Huldrych Zwingli in Switzerland who decided to participate in this European-wide discussion after seeing Luther's postulates; all this would not have happened without the events of 31 October 1517. Theological conversations caught on with French priest John Calvin joining it soon after Zwingli.

Our roots are deep in the Anglican tradition: Both John and Charles Wesley were priests in the Church of England. There are a number of reasons we should observe the day. The themes of the Reformation remain the great themes and principles of our own faith today. The great schism that occurred in the church remains with us. Our fractured denominations have entered into dialogue and cooperative activities that have brought us closer together. Today we may observe Reformation Day with a sense of moving toward unity and community. It is an opportunity to repent of the sins and excesses of the past and to celebrate our common faith, even if we still cannot celebrate a common ritual and sacrament. Reformation today can represent healing of old wounds as, together, we all work to build and strengthen Christ's church and love one another as Christ has loved us.[42]

^"Johann Tetzel," Encyclopædia Britannica, 2007: "Tetzel's experiences as a preacher of indulgences, especially between 1503 and 1510, led to his appointment as general commissioner by Albrecht, archbishop of Mainz, who, deeply in debt to pay for a large accumulation of benefices, had to contribute a considerable sum toward the rebuilding of St. Peter's Basilica in Rome. Albrecht obtained permission from Pope Leo X to conduct the sale of a special plenary indulgence (i.e., remission of the temporal punishment of sin), half of the proceeds of which Albrecht was to claim to pay the fees of his benefices. In effect, Tetzel became a salesman whose product was to cause a scandal in Germany that evolved into the greatest crisis (the Reformation) in the history of the Western church."

^Iserloh, Erwin. The Theses Were Not Posted. Toronto: Saunders of Toronto, Ltd., 1966; Derek Wilson, Out of the Storm: The Life and Legacy of Martin Luther, London: Hutchinson, 2007, ISBN978-0-09-180001-7, 96.

^MacKinnon, Angus (25 January 2016). "500 years after reformation, Pope knocks on Lutherans' door". Yahoo News. Retrieved 22 February 2017. Pope Francis will celebrate the 500th anniversary of the Reformation by attending an ecumenical service in Sweden as a guest of the Lutheran church, the Vatican said Monday. In a highly symbolic act of reconciliation that would even recently have been unthinkable for a Catholic pontiff, Francis will visit the Swedish city of Lund on October 31 for a commemoration jointly organised by his own inter-faith agency and the Lutheran World Federation (LWF).